Skip to ContentSkip to Navigation
How to find us T. (Tirna) Deb

T. Deb

PhD student

1. Neutral Hydrogen gas in the striking Jellyfish Galaxy JO204:

We present JVLA-C observations of the HI gas in JO204, one of the most striking jellyfish galaxies from the GASP survey. JO204 is a massive galaxy in the low-mass cluster Abell 957 at z=0.04243. The HI map reveals an extended 90 kpc long ram-pressure stripped tail of neutral gas, stretching beyond the 30 kpc long ionized gas tail and pointing away from the cluster center. The HI mass seen in emission is (1.32±0.13)×109M⊙, mostly located in the tail. The northern part of the galaxy disk has retained some HI gas, while the southern part has already been completely stripped and displaced into an extended unilateral tail. Comparing the distribution and kinematics of the neutral and ionized gas in the tail indicates a highly turbulent medium.Moreover, we observe associated HI absorption against the 11 mJy central radio continuum source with an estimated HI absorption column density of 3.2 × 1020cm2 .The absorption profile is significantly asymmetric with a wing towards higher velocities. We modelled the HI absorption by assuming that the HI and ionized gas disks have the same kinematics in front of the central continuum source, and deduced a wider absorption profile than observed. The observed asymmetric absorption profile can therefore be explained by a clumpy, rotating HI gas disk seen partially in front of the central continuum source, or by ram-pressure pushing the neutral gas towards the center of the continuum source, triggering the AGN activity.

2. Mapping HI in Abell 2626 and the tentacles of ‘jellyfish’ JW100. I. Data release and catalogue

In this work, we present the results of a 21 cm HI-line imaging survey of A2626, a galaxy cluster embedded in the southern part of the extensive Perseus-Pegasus filament. There are two sub-structures identified in the outskirts of A2626 - one to the NE of the cluster and the other to the SW - that are likely falling into A2626 and within which ‘pre-processing’ of their constituent galaxies may have happened. Of particular interest are six galaxies identified by Poggianti+2016 with a ‘jellyfish’ morphology that are affected by ram-pressure stripping (RPS) of which four are spectroscopically confirmed members of A2626.  I am collaborating with another PhD student from RuG, Julia Healy for this work.

3. HI view of JW100 and other jellyfish candidates in A2626

JW100 is a wonderful laboratory to study star formation under the influence of gas stripping, involving different gas phases, gas heating and AGN activity. A preliminary analysis of new MeerKAT HI data shows that the HI tail of JW100 is more extended than the Halpha, CO, UV, X-ray and radio synchrotron emission in the tail. JW100 is possibly also affected by tidal interactions.

4. HI morphologies and kinematics of galaxies in A2626

In the hierarchical structure formation framework, clusters grow by accretion of galaxies, galaxy groups and other clusters along the filaments of the cosmic web. The result of gravitational and hydrodynamical interactions among galaxies and between galaxies and the cluster, can lead to the removal of cold gas reservoirs from galaxies, eventually quenching their star formation. These processes result in a decrease in the fraction of late-type galaxies and a relative increase of the early-type galaxy population. Consequently, a connection between the star formation history and the cold, diffuse neutral hydrogen gas content of galaxies is expected. Our aim is to obtain a HI perspective on the origin of the Morphology-Density relation and the mechanisms that are responsible for the morphological transformation of galaxies in different cosmic environments. Using recently obtained HI data from MeerKAT on the cluster Abell 2626 and its two sub-clusters, we are studying in detail the spatially resolved morphologies and kinematics of more than 100 HI-detected galaxies, including six jellyfish galaxy candidates, covering a range of cosmic environments. The relative importance and effect of the various physical mechanisms that are responsible for reshaping galaxies as they fall into Abell 2626 are being investigated by analysing the HI and optical morphologies and kinematics of individual galaxies in detail and relate those characteristics to astrophysical mechanisms such as ram-pressure stripping, tidal interaction, harassment etc.


prof. dr. M.A.W. (Marc) Verheijen 

prof. dr. B.M. (Bianca) Poggianti

Last modified:27 June 2020 2.20 p.m.

Contact information

Landleven 12
9747 AD Groningen
The Netherlands